GB 2 136 352 A describes a production process for the production of a sealing film provided with a hologram as a security feature. In that case after the operation of embossing a diffractive relief structure a plastic film is metallised over its full area and then demetallised in region-wise fashion in accurate register relationship with the embossed diffractive relief structure.
Demetallisation in accurate register relationship is costly and the degree of resolution which can be achieved is limited by the adjustment tolerances and the procedure employed.
EP 0 537 439 B2 describes processes for the production of a security element with filigree patterns. The patterns are formed from diffractive structures covered with a metal layer and surrounded by transparent regions in which the metal layer is removed. It is provided that the outline of the filigree pattern is introduced in the form of a depression into a metal-coated carrier material, in that case at the same time the bottom of the depressions is provided with the diffractive structures and then the depressions are filled with a protective lacquer. Excess protective lacquer is to be removed by a scraper blade. After application of the protective lacquer, it is provided that the metal layer is removed by etching in the unprotected transparent regions. The depressions are between about 1 μm and 5 μm while the diffractive structures can involve height differences of more than 1 μm. That process which, in repetition steps, requires adjustment steps for orientation in accurate register relationship, fails when dealing with finer structures. In addition continuous metallic regions covering an area are difficult to implement as the ‘spacers’ are missing, for the operation of scraping off the protective lacquer.